In addition to being a risk factor for HIV infection, drug abuse can have a profound impact on the immunologic responses necessary for control of HIV replication. For example, CD8+ T cell-mediated immunity, which is critical for suppression of productive infection by HIV, is severely hampered by morphine. The goal of this research is to lay the foundation for mechanistic studies into how morphine regulates CD4+ T cell activation and differentiation. CD4+ T cell differentiation into the Th1 lineage and the subsequent activation and differentiation of HIV-specific CD8+ T cells is required for successful vaccination against HIV. Thus, accomplishing our goal will enable us to better understand how opiates might impair the efficacy of HIV vaccines. This understanding will better enable us to counsel prospective recipients of an HIV vaccine. We hypothesize that morphine induces permanent changes within naive CD4+ T cells such that, upon antigenic stimulation, the cells are "pre-programmed" to differentiate into the Th2 lineage. This hypothesis is based on our work using rhesus macaques that have been treated with morphine and infected with SIV. These monkeys were unable to mount a CD8+ T cell-mediated immune response. In addition, published reports showed that morphine can augment IL-4 production by CD4+ T cells in culture. To examine the effects of morphine on CD4+ T cell differentiation, we are combining the use of transgenic T cell receptor models with direct examination of the effects of morphine on immune responses to an HIV vaccine. In this way, we will be able to relate detailed mechanistic studies of the effects of morphine on T cell-mediated immune responses to clinically relevant effects of morphine on HIV vaccine efficacy. In specific aim 1, we will use a mouse line expressing an MHC class II-restricted T cell receptor (TCR) to examine the effects of morphine on Th1/Th2 lineage commitment. We will examine how concurrent administration of morphine and antigenic challenge affects Th1/Th2 differentiation in vivo. Then, we will test whether prior morphine treatment can alter Th1/Th2 differentiation following antigenic challenge. We will also examine whether the changes in Th1/Th2 lineage commitment can be reversed by altering the cytokine environment. In specific aim 2, we will examine CD8+ T cell-mediated immune responses to a DNA vaccine against HIV. Currently, DNA vaccines against HIV are the most likely candidates for human use. We will examine the effects of concurrent or previous use of morphine on the immune responses elicited by a DNA vaccine against HIV. We will also determine the minimal dosing interval of morphine required to impair CD8+ T cell-mediated immunity. Accomplishing these aims will lay the foundation for detailed mechanistic studies into the effects of morphine in vivo. PUBLIC HEALTH RELEVANCE: The use of morphine and other drugs of abuse is a significant risk factor for HIV infection. Further, morphine has dramatic immunoregulatory properties that can impair the efficacy of vaccines against HIV. Our goal is to understand the mechanisms by which morphine can influence the immune responses required for control of HIV replication.